Naturalist Stephen R. Swinburne traces the development of scientific knowledge about the behavior of wolves in the wild and describes the efforts of contemporary wildlife biologists who are introducing the gray wolf back into Yellowstone National Park. This movement, begun by Aldo Leopold in the 1930s, has always faced strong opposition from area ranchers and from others who hold to the longstanding human hatred of wolves. Dramatic color photographs by Jim Brandenburg illustrate the narrative by showing the scientists at work and the wolves in their natural habitat. (Ages 7-14)